Urgent reads and using data source health to determine error recovery procedures

ABSTRACT

A computing device includes an interface configured to interface and communicate with a dispersed storage network (DSN), a memory that stores operational instructions, and processing circuitry operably coupled to the interface and to the memory. The processing circuitry is configured to execute the operational instructions to perform various operations and functions. The computing device determine status of a set of memory devices of one or more sets of storage units (SUs) that distributedly store a set of encoded data slices (EDSs) within the DSN. The computing device detects one or more memory devices thereof that are failing and determines a number of available EDSs. When an insufficient number of EDSs are available, the computing device issues urgent read slice request(s) to recover additional available EDS(s) and facilitate temporary storage thereof within the DSN.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. § 120 as a continuation-in-part (CIP) of U.S. Utility patentapplication Ser. No. 14/986,279, entitled “STORING DATA IN A DISPERSEDSTORAGE NETWORK,” filed Dec. 31, 2015, pending, which claims prioritypursuant to 35 U.S.C. § 119(e) to U.S. Provisional Application No.62/121,667, entitled “SELECTING A STORAGE POOL OF A DISPERSED STORAGENETWORK,” filed Feb. 27, 2015, both of which are hereby incorporatedherein by reference in their entirety and made part of the present U.S.Utility Patent Application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.

Prior art data storage systems do not have acceptable mechanisms bywhich data may be preserved from failed and/or failing componentstherein. The prior art can suffer from total loss of information anddata when components therein fail. There continues to be a need forimprovements in the manner by which data storage systems operate andfunction.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed ordistributed storage network (DSN) in accordance with the presentinvention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an errorencoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an errorencoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of anencoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an errordecoding function in accordance with the present invention;

FIG. 9 is a schematic block diagram of another embodiment of a dispersedstorage network (DSN) in accordance with the present invention;

FIG. 10 is a flowchart illustrating an example of selecting a dataintegrity maintenance process in accordance with the present invention;and

FIG. 11 is a diagram illustrating an embodiment of a method forexecution by one or more computing devices in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, ordistributed, storage network (DSN) 10 that includes a plurality ofcomputing devices 12-16, a managing unit 18, an integrity processingunit 20, and a DSN memory 22. The components of the DSN 10 are coupledto a network 24, which may include one or more wireless and/or wirelined communication systems; one or more non-public intranet systemsand/or public internet systems; and/or one or more local area networks(LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may belocated at geographically different sites (e.g., one in Chicago, one inMilwaukee, etc.), at a common site, or a combination thereof. Forexample, if the DSN memory 22 includes eight storage units 36, eachstorage unit is located at a different site. As another example, if theDSN memory 22 includes eight storage units 36, all eight storage unitsare located at the same site. As yet another example, if the DSN memory22 includes eight storage units 36, a first pair of storage units are ata first common site, a second pair of storage units are at a secondcommon site, a third pair of storage units are at a third common site,and a fourth pair of storage units are at a fourth common site. Notethat a DSN memory 22 may include more or less than eight storage units36. Further note that each storage unit 36 includes a computing core (asshown in FIG. 2, or components thereof) and a plurality of memorydevices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and theintegrity processing unit 20 include a computing core 26, which includesnetwork interfaces 30-33. Computing devices 12-16 may each be a portablecomputing device and/or a fixed computing device. A portable computingdevice may be a social networking device, a gaming device, a cell phone,a smart phone, a digital assistant, a digital music player, a digitalvideo player, a laptop computer, a handheld computer, a tablet, a videogame controller, and/or any other portable device that includes acomputing core. A fixed computing device may be a computer (PC), acomputer server, a cable set-top box, a satellite receiver, a televisionset, a printer, a fax machine, home entertainment equipment, a videogame console, and/or any type of home or office computing equipment.Note that each of the managing unit 18 and the integrity processing unit20 may be separate computing devices, may be a common computing device,and/or may be integrated into one or more of the computing devices 12-16and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to supportone or more communication links via the network 24 indirectly and/ordirectly. For example, interface 30 supports a communication link (e.g.,wired, wireless, direct, via a LAN, via the network 24, etc.) betweencomputing devices 14 and 16. As another example, interface 32 supportscommunication links (e.g., a wired connection, a wireless connection, aLAN connection, and/or any other type of connection to/from the network24) between computing devices 12 & 16 and the DSN memory 22. As yetanother example, interface 33 supports a communication link for each ofthe managing unit 18 and the integrity processing unit 20 to the network24.

Computing devices 12 and 16 include a dispersed storage (DS) clientmodule 34, which enables the computing device to dispersed storage errorencode and decode data as subsequently described with reference to oneor more of FIGS. 3-8. In this example embodiment, computing device 16functions as a dispersed storage processing agent for computing device14. In this role, computing device 16 dispersed storage error encodesand decodes data on behalf of computing device 14. With the use ofdispersed storage error encoding and decoding, the DSN 10 is tolerant ofa significant number of storage unit failures (the number of failures isbased on parameters of the dispersed storage error encoding function)without loss of data and without the need for a redundant or backupcopies of the data. Further, the DSN 10 stores data for an indefiniteperiod of time without data loss and in a secure manner (e.g., thesystem is very resistant to unauthorized attempts at accessing thedata).

In operation, the managing unit 18 performs DS management services. Forexample, the managing unit 18 establishes distributed data storageparameters (e.g., vault creation, distributed storage parameters,security parameters, billing information, user profile information,etc.) for computing devices 12-14 individually or as part of a group ofuser devices. As a specific example, the managing unit 18 coordinatescreation of a vault (e.g., a virtual memory block associated with aportion of an overall namespace of the DSN) within the DSN memory 22 fora user device, a group of devices, or for public access and establishesper vault dispersed storage (DS) error encoding parameters for a vault.The managing unit 18 facilitates storage of DS error encoding parametersfor each vault by updating registry information of the DSN 10, where theregistry information may be stored in the DSN memory 22, a computingdevice 12-16, the managing unit 18, and/or the integrity processing unit20.

The DSN managing unit 18 creates and stores user profile information(e.g., an access control list (ACL)) in local memory and/or withinmemory of the DSN module 22. The user profile information includesauthentication information, permissions, and/or the security parameters.The security parameters may include encryption/decryption scheme, one ormore encryption keys, key generation scheme, and/or dataencoding/decoding scheme.

The DSN managing unit 18 creates billing information for a particularuser, a user group, a vault access, public vault access, etc. Forinstance, the DSN managing unit 18 tracks the number of times a useraccesses a non-public vault and/or public vaults, which can be used togenerate a per-access billing information. In another instance, the DSNmanaging unit 18 tracks the amount of data stored and/or retrieved by auser device and/or a user group, which can be used to generate aper-data-amount billing information.

As another example, the managing unit 18 performs network operations,network administration, and/or network maintenance. Network operationsincludes authenticating user data allocation requests (e.g., read and/orwrite requests), managing creation of vaults, establishingauthentication credentials for user devices, adding/deleting components(e.g., user devices, storage units, and/or computing devices with a DSclient module 34) to/from the DSN 10, and/or establishing authenticationcredentials for the storage units 36. Network administration includesmonitoring devices and/or units for failures, maintaining vaultinformation, determining device and/or unit activation status,determining device and/or unit loading, and/or determining any othersystem level operation that affects the performance level of the DSN 10.Network maintenance includes facilitating replacing, upgrading,repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missingencoded data slices. At a high level, the integrity processing unit 20performs rebuilding by periodically attempting to retrieve/list encodeddata slices, and/or slice names of the encoded data slices, from the DSNmemory 22. For retrieved encoded slices, they are checked for errors dueto data corruption, outdated version, etc. If a slice includes an error,it is flagged as a ‘bad’ slice. For encoded data slices that were notreceived and/or not listed, they are flagged as missing slices. Badand/or missing slices are subsequently rebuilt using other retrievedencoded data slices that are deemed to be good slices to produce rebuiltslices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface module 60, at least one IO device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). The DSNinterface module 76 and/or the network interface module 70 may functionas one or more of the interface 30-33 of FIG. 1. Note that the IO deviceinterface module 62 and/or the memory interface modules 66-76 may becollectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data. When a computing device 12 or 16 has data tostore it disperse storage error encodes the data in accordance with adispersed storage error encoding process based on dispersed storageerror encoding parameters. The dispersed storage error encodingparameters include an encoding function (e.g., information dispersalalgorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding,non-systematic encoding, on-line codes, etc.), a data segmentingprotocol (e.g., data segment size, fixed, variable, etc.), and per datasegment encoding values. The per data segment encoding values include atotal, or pillar width, number (T) of encoded data slices per encodingof a data segment i.e., in a set of encoded data slices); a decodethreshold number (D) of encoded data slices of a set of encoded dataslices that are needed to recover the data segment; a read thresholdnumber (R) of encoded data slices to indicate a number of encoded dataslices per set to be read from storage for decoding of the data segment;and/or a write threshold number (W) to indicate a number of encoded dataslices per set that must be accurately stored before the encoded datasegment is deemed to have been properly stored. The dispersed storageerror encoding parameters may further include slicing information (e.g.,the number of encoded data slices that will be created for each datasegment) and/or slice security information (e.g., per encoded data sliceencryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as theencoding function (a generic example is shown in FIG. 4 and a specificexample is shown in FIG. 5); the data segmenting protocol is to dividethe data object into fixed sized data segments; and the per data segmentencoding values include: a pillar width of 5, a decode threshold of 3, aread threshold of 4, and a write threshold of 4. In accordance with thedata segmenting protocol, the computing device 12 or 16 divides the data(e.g., a file (e.g., text, video, audio, etc.), a data object, or otherdata arrangement) into a plurality of fixed sized data segments (e.g., 1through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more).The number of data segments created is dependent of the size of the dataand the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a datasegment using the selected encoding function (e.g., Cauchy Reed-Solomon)to produce a set of encoded data slices. FIG. 4 illustrates a genericCauchy Reed-Solomon encoding function, which includes an encoding matrix(EM), a data matrix (DM), and a coded matrix (CM). The size of theencoding matrix (EM) is dependent on the pillar width number (T) and thedecode threshold number (D) of selected per data segment encodingvalues. To produce the data matrix (DM), the data segment is dividedinto a plurality of data blocks and the data blocks are arranged into Dnumber of rows with Z data blocks per row. Note that Z is a function ofthe number of data blocks created from the data segment and the decodethreshold number (D). The coded matrix is produced by matrix multiplyingthe data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encodingwith a pillar number (T) of five and decode threshold number of three.In this example, a first data segment is divided into twelve data blocks(D1-D12). The coded matrix includes five rows of coded data blocks,where the first row of X11-X14 corresponds to a first encoded data slice(EDS 1_1), the second row of X21-X24 corresponds to a second encodeddata slice (EDS 2_1), the third row of X31-X34 corresponds to a thirdencoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to afourth encoded data slice (EDS 4_1), and the fifth row of X51-X54corresponds to a fifth encoded data slice (EDS 5_1). Note that thesecond number of the EDS designation corresponds to the data segmentnumber.

Returning to the discussion of FIG. 3, the computing device also createsa slice name (SN) for each encoded data slice (EDS) in the set ofencoded data slices. A typical format for a slice name 60 is shown inFIG. 6. As shown, the slice name (SN) 60 includes a pillar number of theencoded data slice (e.g., one of 1-T), a data segment number (e.g., oneof 1-Y), a vault identifier (ID), a data object identifier (ID), and mayfurther include revision level information of the encoded data slices.The slice name functions as, at least part of, a DSN address for theencoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces aplurality of sets of encoded data slices, which are provided with theirrespective slice names to the storage units for storage. As shown, thefirst set of encoded data slices includes EDS 1_1 through EDS 5_1 andthe first set of slice names includes SN 1_1 through SN 5_1 and the lastset of encoded data slices includes EDS 1_Y through EDS 5_Y and the lastset of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of a data object that was dispersed storage error encodedand stored in the example of FIG. 4. In this example, the computingdevice 12 or 16 retrieves from the storage units at least the decodethreshold number of encoded data slices per data segment. As a specificexample, the computing device retrieves a read threshold number ofencoded data slices.

To recover a data segment from a decode threshold number of encoded dataslices, the computing device uses a decoding function as shown in FIG.8. As shown, the decoding function is essentially an inverse of theencoding function of FIG. 4. The coded matrix includes a decodethreshold number of rows (e.g., three in this example) and the decodingmatrix in an inversion of the encoding matrix that includes thecorresponding rows of the coded matrix. For example, if the coded matrixincludes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2,and 4, and then inverted to produce the decoding matrix.

In some examples, note that dispersed or distributed storage network(DSN) memory includes one or more of a plurality of storage units (SUs)such as SUs 36 (e.g., that may alternatively be referred to adistributed storage and/or task network (DSTN) module that includes aplurality of distributed storage and/or task (DST) execution units 36that may be located at geographically different sites (e.g., one inChicago, one in Milwaukee, etc.). Each of the SUs (e.g., alternativelyreferred to as DST execution units in some examples) is operable tostore dispersed error encoded data and/or to execute, in a distributedmanner, one or more tasks on data. The tasks may be a simple function(e.g., a mathematical function, a logic function, an identify function,a find function, a search engine function, a replace function, etc.), acomplex function (e.g., compression, human and/or computer languagetranslation, text-to-voice conversion, voice-to-text conversion, etc.),multiple simple and/or complex functions, one or more algorithms, one ormore applications, etc.

FIG. 9 is a schematic block diagram of another embodiment of a dispersedstorage network (DSN) in accordance with the present invention. Thisdiagram includes a schematic block diagram of another embodiment of adispersed storage network (DSN) that includes the computing device 16 ofFIG. 1, the network 24 of FIG. 1, and a storage unit (SU) pool 940. Thecomputing device 16 includes the DS client module 34 of FIG. 1. The SUpool 940 includes a set of SUs 1-n. Each SU includes a set of Mmemories.

The DSN functions to select a data integrity maintenance process formaintaining integrity of stored data within the SU pool 940. In anexample of operation of the selecting of the data integrity maintenanceprocess, the DS client module 34 detects one or more failing memorydevices of a set of memory devices associated with a DSN address range,where a plurality of DSN address ranges 1-M are associated with the setof SUs. The detecting includes at least one of interpreting a receivederror message, initiating a query, receiving a query response,initiating a memory test, and interpreting a memory test result.

The plurality of DSN address ranges 1-M includes the DSN address range,where a data object is stored as a plurality of sets of encoded dataslices in at least one set of memory devices. The data object is dividedinto a plurality of data segments where each data segment is dispersedstorage error encoded to produce a set of encoded data slices forstoring in a corresponding set of memory devices. For example, the DSclient module 34 receives error messages indicating that memories 1-2and 2-2 are failing of the set of memory devices associated with the DSNaddress range 2.

For a data segment of the plurality of data segments, the DS clientmodule 34 determines a number of available encoded data slices of acorresponding set of encoded data slices stored in a corresponding setof memory devices. The determining includes at least one of interpretinga list of slice responses, interpreting read slice responses, andinterpreting one or more error messages.

When the number of available encoded data slices compares unfavorably toa rebuilding threshold level (e.g., less than the rebuilding thresholdlevel), the DS client module 34 initiates a data salvaging process torecover encoded data slices of the set of encoded data slices from thecorresponding failing memory devices. For example, the DS client module34 issues, via the network 24, urgent read slice requests 920 for theencoded data slices to be recovered to the SUs corresponding to thefailing memory devices. For instance, the DS client module 34 issues,via the network 24, the urgent read slice requests 920 to SUs 1 and 2 toquickly recover recoverable encoded data slices from the memories 1-2,and 2-2. SUs receiving a corresponding urgent read slice requestprioritizes issuing a corresponding urgent read slice response. Theprioritizing includes one or more of de-prioritizing one or more ofother access requests (e.g., data access requests 910) and maintenancetasks and raising priority of execution of tasks related to issuing theurgent read slice response (e.g., SU 1 immediately accesses the memory1-2 to recover encoded data slices prior to a complete failure of thememory 1-2).

Having issued the urgent read slice request, the DS client module 34receives, via the network 24, urgent read slice responses 930. Havingreceived the urgent read slice responses 930, the DS client module 34facilitates temporary storage of encoded data slices extracted from thereceived urgent read slice responses 930. For example, the DS clientmodule 34 sends the extracted encoded data slices to another SU fortemporary storage.

In an example of operation and implementation, a computing deviceincludes an interface configured to interface and communicate with adispersed or distributed storage network (DSN), a memory that storesoperational instructions, and a processing module, processor, and/orprocessing circuitry operably coupled to the interface and memory. Theprocessing module, processor, and/or processing circuitry is configuredto execute the operational instructions to perform various operations,functions, etc. In some examples, the processing module, processor,and/or processing circuitry, when operable within the computing devicebased on the operational instructions, is configured to perform variousoperations, functions, etc. In certain examples, the processing module,processor, and/or processing circuitry, when operable within thecomputing device is configured to perform one or more functions that mayinclude generation of one or more signals, processing of one or moresignals, receiving of one or more signals, transmission of one or moresignals, interpreting of one or more signals, etc. and/or any otheroperations as described herein and/or their equivalents.

In an example of operation and implementation, a computing device (e.g.,computing device 16 of FIG. 1, FIG. 9, and/or any other diagram,example, embodiment, equivalent, etc. as described herein) is configuredto determine status of a set of memory devices of one or more sets ofstorage units (SUs) that distributedly store a set of encoded dataslices (EDSs) within the DSN. Note that a data object is segmented intoa plurality of data segments, and a data segment of the plurality ofdata segments is dispersed error encoded in accordance with dispersederror encoding parameters to produce the set of EDSs.

The computing device is also configured to process the status of the setof memory devices of the one or more sets of SUs to detect one or morememory devices thereof that are failing based on at least one criterion.The computing device is also configured to determine a number ofavailable EDSs of the set of EDSs among the set of memory devices of theone or more sets of SUs.

When the number of available EDSs of the set of EDSs comparesunfavorably to a data segment rebuild threshold level, the computingdevice is also configured to issue at least one urgent read slicerequest to at least one SU of the one or more sets of SUs that isassociated with at least one of the one or more memory devices that isfailing to recover at least one additional available EDS of the set ofEDSs there from.

The computing device is also configured to receive the at least oneadditional available EDS of the set of EDSs from the at least one of theone or more memory devices that is failing and to facilitate temporarystorage of the at least one additional available EDS of the set of EDSswithin the DSN.

In some examples, the computing device is also configured to detect theone or more memory devices thereof that are failing based on at leastone criterion including based on interpreting a received error message,initiating a query, receiving a query response, initiating a memorytest, and/or interpreting a memory test result.

In even other examples, the computing device is also configured todetermine the number of available EDSs of the set of EDSs among the setof memory devices of the one or more sets of SUs based on interpreting alist of slice responses, interpreting read slice responses, and/orinterpreting one or more error messages.

In yet other examples, when the number of available EDSs of the set ofEDSs compares unfavorably to the data segment rebuild threshold level,the computing device is also configured to issue a plurality of urgentread slice requests to a plurality of SUs of the one or more sets of SUsthat is associated with the at least one of the one or more memorydevices that is failing to recover a plurality of additional availableEDSs of the set of EDSs there from. The computing device is alsoconfigured to prioritize the plurality of urgent read slice requestsbased on deprioritizing one or more of other access requests ormaintenance tasks and raising priority of execution of tasks related toissuing the plurality of urgent read slice requests.

In some examples, with respect to a data object, the data object issegmented into a plurality of data segments, and a data segment of theplurality of data segments is dispersed error encoded in accordance withdispersed error encoding parameters to produce a set of encoded dataslices (EDSs) (e.g., in some instances, the set of EDSs aredistributedly stored in a plurality of storage units (SUs) within theDSN). In some examples, the set of EDSs is of pillar width. Also, withrespect to certain implementations, note that the decode thresholdnumber of EDSs are needed to recover the data segment, and a readthreshold number of EDSs provides for reconstruction of the datasegment. Also, a write threshold number of EDSs provides for asuccessful transfer of the set of EDSs from a first at least onelocation in the DSN to a second at least one location in the DSN. Theset of EDSs is of pillar width and includes a pillar number of EDSs.Also, in some examples, each of the decode threshold, the readthreshold, and the write threshold is less than the pillar number. Also,in some particular examples, the write threshold number is greater thanor equal to the read threshold number that is greater than or equal tothe decode threshold number.

Note that the computing device as described herein may be located at afirst premises that is remotely located from a second premisesassociated with at least one other SU, dispersed storage (DS) unit,computing device, at least one SU of a plurality of SUs within the DSN(e.g., such as a plurality of SUs that are implemented to storedistributedly a set of EDSs), etc. In addition, note that such acomputing device as described herein may be implemented as any of anumber of different devices including a managing unit that is remotelylocated from another SU, DS unit, computing device, etc. within the DSNand/or other device within the DSN, an integrity processing unit that isremotely located from another computing device and/or other devicewithin the DSN, a scheduling unit that is remotely located from anothercomputing device and/or SU within the DSN, and/or other device. Also,note that such a computing device as described herein may be of any of avariety of types of devices as described herein and/or their equivalentsincluding a DS unit and/or SU included within any group and/or set of DSunits and/or SUs within the DSN, a wireless smart phone, a laptop, atablet, a personal computers (PC), a work station, and/or a video gamedevice, and/or any type of computing device or communication device.Also, note also that the DSN may be implemented to include and/or bebased on any of a number of different types of communication systemsincluding a wireless communication system, a wire lined communicationsystem, a non-public intranet system, a public internet system, a localarea network (LAN), and/or a wide area network (WAN). Also, in someexamples, any device configured to support communications within such aDSN may be also be configured to and/or specifically implemented tosupport communications within a satellite communication system, awireless communication system, a wired communication system, afiber-optic communication system, and/or a mobile communication system(and/or any other type of communication system implemented using anytype of communication medium or media).

FIG. 10 is a flowchart illustrating an example of selecting a dataintegrity maintenance process in accordance with the present invention.This diagram includes a flowchart illustrating an example of selecting adata integrity maintenance process. The method 1000 begins or continuesat a step 1010 where a processing module (e.g., of a distributed storage(DS) client module and/or computing device) detects one or more failingmemory devices of a set of memory devices, where a data segment isdispersed storage error encoded to produce a set of encoded data slicesthat are stored in the set of memory devices. The detecting includes oneor more of interpreting an error message, interpreting a query response,interpreting a read slice response, correlating identified failed memorydevices with a common set of memory devices.

The method 1000 continues at the step 1020 where the processing moduledetermines a number of available encoded data slices of the set ofencoded data slices. The determining includes at least one ofidentifying a data object associated with storage of the set of encodeddata slices in the set of memory devices, interpreting list sliceresponses, interpreting read slice responses, and interpreting errormessages.

When the number of available encoded data slices compares unfavorably toa rebuilding threshold level, the method 1000 continues at the step 1030where the processing module issues one or more urgent read slicerequests to storage units associated with at least some of the one ormore failing memory devices to recover available encoded data slicesassociated with the at least some of the feeling memory devices. Theissuing includes at least one of determining that the number ofavailable encoded data slices is less than the rebuilding thresholdlevel, and determining that the number of available encoded data slicesis substantially the same as at least one of a decode threshold numberand a read threshold number. The issuing further includes identifyingthe storage units associated with the failing memory devices associatedwith a set of encoded data slices, generating the one or more urgentread slice request, and sending the generated one or more urgent readslice requests to the identified storage units.

The method 1000 continues at the step 1040 where the processing modulereceives one or more urgent read slice responses that includes one ormore encoded data slices. The method 1000 continues at the step 1050where the processing module facilitates temporary storage of encodeddata slices extracted from the received urgent read slice responses. Forexample, the processing module issues a write slice request to a storageunit associated with an unavailable memory device to store the extractedencoded data slices, where the write slice request includes theextracted encoded data slices.

FIG. 11 is a diagram illustrating an embodiment of a method 1100 forexecution by one or more computing devices in accordance with thepresent invention. The method 1100 operates in step 1110 by determiningstatus of a set of memory devices of one or more sets of storage units(SUs) that distributedly store a set of encoded data slices (EDSs)within a dispersed or distributed storage network (DSN). Note that adata object is segmented into a plurality of data segments, and a datasegment of the plurality of data segments is dispersed error encoded inaccordance with dispersed error encoding parameters to produce the setof EDSs.

The method 1100 then continues in step 1120 by processing the status ofthe set of memory devices of the one or more sets of SUs to detect oneor more memory devices thereof that are failing based on at least onecriterion. The method 1100 operates in step 1130 by determining a numberof available EDSs of the set of EDSs among the set of memory devices ofthe one or more sets of SUs.

When the number of available EDSs of the set of EDSs compares favorablyto a data segment rebuild threshold level (step 1140), the method 1100branches via the yes branch and ends. Alternatively, when the number ofavailable EDSs of the set of EDSs compares unfavorably to a data segmentrebuild threshold level (step 1140), the method 1100 branches via the nobranch to step 1150 by issuing (e.g., via an interface of the computingdevice that is configured to interface and communicate with the DSN) atleast one urgent read slice request to at least one SU of the one ormore sets of SUs that is associated with at least one of the one or morememory devices that is failing to recover at least one additionalavailable EDS of the set of EDSs there from.

The method 1100 then operates in step 1160 by receiving (e.g., via theinterface) the at least one additional available EDS of the set of EDSsfrom the at least one of the one or more memory devices that is failing.The method 1100 operates in step 1170 by facilitating (e.g., via theinterface) temporary storage of the at least one additional availableEDS of the set of EDSs within the DSN.

This disclosure presents, among other things, various novel solutionsthat operate to provide for urgent reads and using data source health todetermine error recovery procedures. For example, when a memory devicefails, a decision must be made as to whether to attempt to salvage asmuch data as possible from the failed memory device or to fail thememory device and begin rebuilding. The advantage of rebuilding is thatit can be faster, while the advantage of salvaging data from the failedmemory device is that it avoids impacting the rest of the system withnetwork and TO required for the rebuilding. However, there is anotherimportant distinction: the latter approach may be the only option toprevent data loss at the point when the data source is at or close toIDA threshold. Therefore, the state of the data sources and health ofthe namespace range of the failed/failing memory device is considered bya storage unit (SU) when determining whether to fail the memory deviceand rebuild, or to attempt a potentially lengthy salvaging procedurefrom the memory device (or some combination of both rebuilding andsalvaging). When a SU determines that sources within the namespace rangeowned by the failing memory device are close to threshold, it will defercompletely failing the drive until as much data as possible has beenrecovered. Additionally, a computing device may issue an“UrgentReadRequest”. An urgent read request may occur only when the readwould otherwise fail due to inability to meet IDA threshold. A normalReadRequest which is routed to a failing memory device may be failedwith an IO error (as attempting to read from a failing memory device maycause severe performance problems and interfere with a salvagingprocedure). However, an UrgentRead request may be issued if the datasource would be below IDA (or read) threshold if the failing memorydevice is not read from. This bypasses normal checks by the SU, and theSU will attempt to read from a failing memory device when an urgent readrequest is received, thus possibly enabling the source to be read.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form a solidstate memory, a hard drive memory, cloud memory, thumb drive, servermemory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A computing device comprising: an interfaceconfigured to interface and communicate with a dispersed or distributedstorage network (DSN); memory that stores operational instructions; andprocessing circuitry operably coupled to the interface and to thememory, wherein the processing circuitry is configured to execute theoperational instructions to: determine status of a set of memory devicesof one or more sets of storage units (SUs) that distributedly store aset of encoded data slices (EDSs) within the DSN, wherein a data objectis segmented into a plurality of data segments, wherein a data segmentof the plurality of data segments is dispersed error encoded inaccordance with dispersed error encoding parameters to produce the setof EDSs; process the status of the set of memory devices of the one ormore sets of SUs to detect one or more memory devices thereof that arefailing based on at least one criterion; determine a number of availableEDSs of the set of EDSs among the set of memory devices of the one ormore sets of SUs; when the number of available EDSs of the set of EDSscompares unfavorably to a data segment rebuild threshold level, issue atleast one urgent read slice request to at least one SU of the one ormore sets of SUs that is associated with at least one of the one or morememory devices that is failing to recover at least one additionalavailable EDS of the set of EDSs there from; receive the at least oneadditional available EDS of the set of EDSs from the at least one of theone or more memory devices that is failing; and facilitate temporarystorage of the at least one additional available EDS of the set of EDSswithin the DSN.
 2. The computing device of claim 1, wherein theprocessing circuitry is further configured to execute the operationalinstructions to: detect the one or more memory devices thereof that arefailing based on at least one criterion including based on at least oneof interpreting a received error message, initiating a query, receivinga query response, initiating a memory test, or interpreting a memorytest result.
 3. The computing device of claim 1, wherein the processingcircuitry is further configured to execute the operational instructionsto: determine the number of available EDSs of the set of EDSs among theset of memory devices of the one or more sets of SUs based on at leastone of interpreting a list of slice responses, interpreting read sliceresponses, or interpreting one or more error messages.
 4. The computingdevice of claim 1, wherein the processing circuitry is furtherconfigured to execute the operational instructions to: when the numberof available EDSs of the set of EDSs compares unfavorably to the datasegment rebuild threshold level, issue a plurality of urgent read slicerequests to a plurality of SUs of the one or more sets of SUs that isassociated with the at least one of the one or more memory devices thatis failing to recover a plurality of additional available EDSs of theset of EDSs there from; and prioritize the plurality of urgent readslice requests based on at least one of deprioritizing one or more ofother access requests and maintenance tasks or raising priority ofexecution of tasks related to issuing the plurality of urgent read slicerequests.
 5. The computing device of claim 1, wherein: a decodethreshold number of EDSs are needed to recover the data segment; a readthreshold number of EDSs provides for reconstruction of the datasegment; a write threshold number of EDSs provides for a successfultransfer of the set of EDSs from a first at least one location in theDSN to a second at least one location in the DSN; the set of EDSs is ofpillar width and includes a pillar number of EDSs; each of the decodethreshold number, the read threshold number, and the write thresholdnumber is less than the pillar number; and the write threshold number isgreater than or equal to the read threshold number that is greater thanor equal to the decode threshold number.
 6. The computing device ofclaim 1, wherein the computing device is located at a first premisesthat is remotely located from a second premises of the at least one SUof the one or more sets of SUs within the DSN.
 7. The computing deviceof claim 1 further comprising: a SU of the one or more sets of SUswithin the DSN, a wireless smart phone, a laptop, a tablet, a personalcomputers (PC), a work station, or a video game device.
 8. The computingdevice of claim 1, wherein the DSN includes at least one of a wirelesscommunication system, a wire lined communication system, a non-publicintranet system, a public internet system, a local area network (LAN),or a wide area network (WAN).
 9. A computing device comprising: aninterface configured to interface and communicate with a dispersed ordistributed storage network (DSN); memory that stores operationalinstructions; and processing circuitry operably coupled to the interfaceand to the memory, wherein the processing circuitry is configured toexecute the operational instructions to: determine status of a set ofmemory devices of one or more sets of storage units (SUs) thatdistributedly store a set of encoded data slices (EDSs) within the DSN,wherein a data object is segmented into a plurality of data segments,wherein a data segment of the plurality of data segments is dispersederror encoded in accordance with dispersed error encoding parameters toproduce the set of EDSs; process the status of the set of memory devicesof the one or more sets of SUs to detect one or more memory devicesthereof that are failing based on at least one criterion including basedon at least one of interpreting a received error message, initiating aquery, receiving a query response, initiating a memory test, orinterpreting a memory test result; determine a number of available EDSsof the set of EDSs among the set of memory devices of the one or moresets of SUs based on at least one of interpreting a list of sliceresponses, interpreting read slice responses, or interpreting one ormore error messages; when the number of available EDSs of the set ofEDSs compares unfavorably to a data segment rebuild threshold level,issue at least one urgent read slice request to at least one SU of theone or more sets of SUs that is associated with at least one of the oneor more memory devices that is failing to recover at least oneadditional available EDS of the set of EDSs there from; receive the atleast one additional available EDS of the set of EDSs from the at leastone of the one or more memory devices that is failing; and facilitatetemporary storage of the at least one additional available EDS of theset of EDSs within the DSN.
 10. The computing device of claim 9, whereinthe processing circuitry is further configured to execute theoperational instructions to: when the number of available EDSs of theset of EDSs compares unfavorably to the data segment rebuild thresholdlevel, issue a plurality of urgent read slice requests to a plurality ofSUs of the one or more sets of SUs that is associated with the at leastone of the one or more memory devices that is failing to recover aplurality of additional available EDSs of the set of EDSs there from;and prioritize the plurality of urgent read slice requests based on atleast one of deprioritizing one or more of other access requests andmaintenance tasks or raising priority of execution of tasks related toissuing the plurality of urgent read slice requests.
 11. The computingdevice of claim 9, wherein: a decode threshold number of EDSs are neededto recover the data segment; a read threshold number of EDSs providesfor reconstruction of the data segment; a write threshold number of EDSsprovides for a successful transfer of the set of EDSs from a first atleast one location in the DSN to a second at least one location in theDSN; the set of EDSs is of pillar width and includes a pillar number ofEDSs; each of the decode threshold number, the read threshold number,and the write threshold number is less than the pillar number; and thewrite threshold number is greater than or equal to the read thresholdnumber that is greater than or equal to the decode threshold number. 12.The computing device of claim 9 further comprising: a SU of the one ormore sets of SUs within the DSN, a wireless smart phone, a laptop, atablet, a personal computers (PC), a work station, or a video gamedevice.
 13. The computing device of claim 9, wherein the DSN includes atleast one of a wireless communication system, a wire lined communicationsystem, a non-public intranet system, a public internet system, a localarea network (LAN), or a wide area network (WAN).
 14. A method forexecution by a computing device, the method comprising: determiningstatus of a set of memory devices of one or more sets of storage units(SUs) that distributedly store a set of encoded data slices (EDSs)within a dispersed or distributed storage network (DSN), wherein a dataobject is segmented into a plurality of data segments, wherein a datasegment of the plurality of data segments is dispersed error encoded inaccordance with dispersed error encoding parameters to produce the setof EDSs; processing the status of the set of memory devices of the oneor more sets of SUs to detect one or more memory devices thereof thatare failing based on at least one criterion; determining a number ofavailable EDSs of the set of EDSs among the set of memory devices of theone or more sets of SUs; when the number of available EDSs of the set ofEDSs compares unfavorably to a data segment rebuild threshold level,issuing, via an interface of the computing device that is configured tointerface and communicate with the DSN, at least one urgent read slicerequest to at least one SU of the one or more sets of SUs that isassociated with at least one of the one or more memory devices that isfailing to recover at least one additional available EDS of the set ofEDSs there from; receiving, via the interface, the at least oneadditional available EDS of the set of EDSs from the at least one of theone or more memory devices that is failing; and facilitating, via theinterface, temporary storage of the at least one additional availableEDS of the set of EDSs within the DSN.
 15. The method of claim 14further comprising: detecting the one or more memory devices thereofthat are failing based on at least one criterion including based on atleast one of interpreting a received error message, initiating a query,receiving a query response, initiating a memory test, or interpreting amemory test result.
 16. The method of claim 14 further comprising:determining the number of available EDSs of the set of EDSs among theset of memory devices of the one or more sets of SUs based on at leastone of interpreting a list of slice responses, interpreting read sliceresponses, or interpreting one or more error messages.
 17. The method ofclaim 14 further comprising: when the number of available EDSs of theset of EDSs compares unfavorably to the data segment rebuild thresholdlevel, issuing a plurality of urgent read slice requests to a pluralityof SUs of the one or more sets of SUs that is associated with the atleast one of the one or more memory devices that is failing to recover aplurality of additional available EDSs of the set of EDSs there from;and prioritizing the plurality of urgent read slice requests based on atleast one of deprioritizing one or more of other access requests ormaintenance tasks and raising priority of execution of tasks related toissuing the plurality of urgent read slice requests.
 18. The method ofclaim 14, wherein: a decode threshold number of EDSs are needed torecover the data segment; a read threshold number of EDSs provides forreconstruction of the data segment; a write threshold number of EDSsprovides for a successful transfer of the set of EDSs from a first atleast one location in the DSN to a second at least one location in theDSN; the set of EDSs is of pillar width and includes a pillar number ofEDSs; each of the decode threshold number, the read threshold number,and the write threshold number is less than the pillar number; and thewrite threshold number is greater than or equal to the read thresholdnumber that is greater than or equal to the decode threshold number. 19.The method of claim 14, wherein the computing device includes a SU ofthe one or more sets of SUs within the DSN, a wireless smart phone, alaptop, a tablet, a personal computers (PC), a work station, or a videogame device.
 20. The method of claim 14, wherein the DSN includes atleast one of a wireless communication system, a wire lined communicationsystem, a non-public intranet system, a public internet system, a localarea network (LAN), or a wide area network (WAN).